Integrated optics is the technology of combining various optical devices and components on a common chip or substrate to transport, focus, multiplex, de-multiplex, split, combine, polarize, isolate, couple, switch, filter, modulate (phase or amplitude), detect, and/or generate light. Optical waveguides and other functional elements alone, or in combination form the optical devices including: optical resonators, arrayed waveguide gratings, couples, splitters, polarization splitters/combiners, polarization rotators, Mach-Zehnder interferometers, multimode interference waveguides, grating, mode transformers, delay lines, optical vias, and the like.
The trend in the field of integrated optics is to densely pack optical devices having varying functions onto a single integrated optical device, such as a planar light-wave circuit, multi-layer planar light-wave circuit, photonic integrated circuit and the like. Densely packing optical devices requires strategic placement of optical waveguides. Generally, the ability to shrink the dimensions of an optical device is limited by the refractive index contrast of the optical waveguides from which it is formed. For example, an optical device is constrained by the minimum allowable radius of curvature of its optical waveguides before the optical waveguide incurs significant optical propagation loss.
Thermal devices are also commonly included within integrated optical devices for heating optical waveguides through the use of local resistive heating elements. Heating manipulates the optical properties of the output signal such as center wavelength, amplitude, phase, and shape. For example, heating an optical waveguide can alter the refractive index affecting the phase of the optical signal propagating through the optical waveguide. Each thermal device requires substantial power consumption to achieve a lucrative response. The trend towards densely packing multiple optical devices utilizing these thermal devices results in an increase in the power demand for the integrated optic device to support the desired functions.